Question

How to create polygons around states in leaflet?

Answer 1

Use addPolygons() to create polygons in a leaflet. See the below example to create polygons.

neStates <- subset(states, states$STUSPS %in% c(
  "CT","ME","MA","NH","RI","VT","NY","NJ","PA"
))

leaflet(neStates) %>%
  addPolygons(color = "#444444", weight = 1, smoothFactor = 0.5,
    opacity = 1.0, fillOpacity = 0.5,
    fillColor = ~colorQuantile("YlOrRd", ALAND)(ALAND),
    highlightOptions = highlightOptions(color = "white", weight = 2,
      bringToFront = TRUE))

See the below manual to create polygons in leaflet.

https://rstudio.github.io/leaflet/shapes.html